Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
  • C08B37/00—Preparation of polysaccharides not provided for in groups C08B1/00 - C08B35/00; Derivatives thereof
  • C08B37/006—Heteroglycans, i.e. polysaccharides having more than one sugar residue in the main chain in either alternating or less regular sequence; Gellans; Succinoglycans; Arabinogalactans; Tragacanth or gum tragacanth or traganth from Astragalus; Gum Karaya from Sterculia urens; Gum Ghatti from Anogeissus latifolia; Derivatives thereof
  • C08B37/0063—Glycosaminoglycans or mucopolysaccharides, e.g. keratan sulfate; Derivatives thereof, e.g. fucoidan
  • C08B37/0075—Heparin; Heparan sulfate; Derivatives thereof, e.g. heparosan; Purification or extraction methods thereof
  • C08B37/0078—Degradation products

Definitions

• the present invention relates to a process for the preparation of low molecular weight heparin. More specifically, the present invention relates to an improved process for the preparation of Enoxaparin sodium.
• Heparins are biologically active agents, extracted from natural sources, and have valuable anticoagulant and antithrombotic properties. In particular, they are useful in the treatment of postoperative venous thrombosis.
• Low molecular weight heparins are prepared by either chemical or enzymatic depolymerization of heparin.
• Low molecular weight (LMW) heparins which are approved and marketed in different countries include Enoxaparin, Dalteparin, Nadroparin, Parnaparin, Tinzaparin, Bemiparin and Certoparin.
• Enoxaparin sodium is manufactured by Sanofi-Aventis and is sold in the form of injection in the United States and Europe, under the tradename Lovenox®/Clexane® respectively.
• Enoxaparin sodium is prepared from heparin sodium derived from porcine intestinal mucosa as starting material, by alkaline depolymerization of heparin benzyl ester salt.
• Enoxaparin sodium preparation that mainly comprises the steps of preparation of benzethonium heparinate, preparation of heparin benzyl ester sodium salt and alkaline depolymerization of the heparin benzyl ester sodium salt.
• the present invention provides an improved process for the preparation of Enoxaparin sodium, comprising the steps of:
• the present invention provides a process for the preparation of Enoxaparin sodium, comprising the steps of:
• the benzethonium heparinate may be prepared by the interaction of a stoichiometric excess of the benzethonium chloride with heparin sodium, in an aqueous medium, at a temperature of 20° C. to 40° C.
• the inert solvent used for dissolving the heparin benzethonium salt is selected from N, N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), methylene chloride (DCM) and the like.
• the ratio of benzethonium heparinate, inert solvent and benzyl Chloride may range from 1:2:1 to 1:6:1.
• the reaction of heparin benzethonium salt with benzyl chloride is carried out at a temperature in the range of room temperature to 70° C. for a period of 1 to 20 hours, preferably at 30 to 55° C. for 5 to 15 h.
• room temperature means temperature in the range of 18° C. and 35° C.
• the heparin benzyl ester obtained as per the prior art processes is a hard and sticky mass which is difficult to extract from the process equipment and requires large volumes of alcoholic sodium acetate solution, resulting in significant yield loss.
• step (b) addition of water to the reaction mixture containing crude heparin benzyl ester obtained in step (b) is carried out at a temperature of 0 to 25° C. for 15 min to 4 hours.
• step (b) addition of water to the reaction mixture containing crude heparin benzyl ester obtained in step (b) is carried out at a temperature of 0 to 25° C. for 15 min to 4 hours.
• step (b) for 1 Kg of crude heparin benzyl ester, 7 liters of methanolic sodium acetate solution is used.
• addition of water to the reaction mixture containing crude heparin benzyl ester is carried out at a temperature of 10 to 20° C.
• the heparin benzyl ester in the form of sodium salt is isolated by adding alcoholic solution of sodium acetate, wherein the alcohol is selected from methanol, propanol, isopropanol and mixtures thereof.
• step (e) depolymerization is carried out by treating the heparin benzyl ester sodium salt with an inorganic base in an aqueous solution.
• the inorganic base is an alkaline hydroxide such as sodium hydroxide.
• the ratio of an inorganic base to heparin benzyl ester sodium salt may range from 0.05 to 0.2 by weight, and preferably from 0.08 to 0.15 by weight.
• the depolymerization is carried out at a temperature of 50° C. to 70° C., preferably 55° C. to 65° C. for 30 minutes to 3 hours, preferably 1 to 2 hours.
• the depolymerization of one part by weight of heparin benzyl ester sodium salt is admixed with 0.08 to 0.15 part by weight of sodium hydroxide, as well as with 20 to 30 parts by weight of water, and the resulting admixture is then maintained at a temperature of 55° C. to 65° C. for 1 to 2 hours to get crude Enoxaparin sodium.
• the crude Enoxaparin sodium is then subjected to bleaching (step (f)) to get decolorized Enoxaparin sodium.
• the color of the Enoxaparin sodium is improved by using 30% hydrogen peroxide at a pH of about 9-10.
• the resultant product is colorless or white.
• bleaching step is performed by adjusting the pH to about 9-10, adding 30% hydrogen peroxide solution, stirring the mixture for about 45 minutes to 90 minutes by maintaining the pH constantly at about 9-10, readjusting the pH to 6-7, adding sodium chloride at a concentration of 5-15% (w/v) followed by precipitation with alcohol (such as methanol and ethanol).
• bleaching step is performed by adjusting the pH to about 9.7 ⁇ 1, adding 30% hydrogen peroxide solution, stirring the mixture for about 60 minutes by maintaining the pH constantly at about 9.7 ⁇ 1, readjusting the pH to 6.0 ⁇ 0.1, adding sodium chloride at a concentration of about 10% (w/v) followed by precipitation with methanol (3.6 volumes), The precipitated product is then filtered and dried under vacuum at 55° C. for 9 hours to obtain decolorized enoxaparin sodium.
• the decolorized product obtained after bleaching step is purified by dissolving in water, adding sodium chloride, precipitating by methanol and filtering to obtain pure Enoxaparin sodium.
• the purified Enoxaparin sodium is lyophilized by dissolving in a mixture of water and alcohol to obtain Enoxaparin sodium in powder form.
• the alcohol is selected from a group comprising methanol, ethanol, isopropanol and a mixture thereof.
• the solvent is a mixture of water and ethanol.
• the lyophilization is carried out by dissolving pure Enoxaparin sodium in a mixture of solvent containing water at a concentration of 85 to 95% (v/v) and alcohol at a concentration of and 5 to 15% (v/v) respectively. If water alone is used as described in the prior art, then it requires more lyophilization time and yields Enoxaparin sodium as a cake with residual moisture.
• the present invention provides a process for the preparation of enoxaparin sodium, which comprises the steps of:
• the process of the present invention is useful for producing Enoxaparin sodium having average molecular weight between 4000 and 5500 daltons and with 12% to 20% of fractions having a molecular weight less than 2000 daltons and 68% and 88% of fractions having a molecular weight within the range 2000 to 8000 daltons.
• Enoxaparin sodium prepared according to the present invention meets the United States Pharmacopoeial requirement as well as sameness criteria with respect to equivalence of physicochemical properties, mode of depolymerisation and equivalence in disaccharide building blocks, fragment mapping, and sequence of oligosaccharide species.
• Examples 1-4 represent the preparation of heparin benzyl ester or its salts in accordance with the invention.
• Step a 1718 g of water and 275 g of benzethonium chloride were fed into a round bottom flask and stirred till dissolution at room temperature. 1000 g of water and 100 g of heparin sodium were fed into another round bottom flask and stirred for dissolution. A solution of benzethonium chloride in water was added slowly to heparin sodium solution and maintained for 2.5 hours. Then, the reaction mass was filtered, and the cake obtained was washed with water repeatedly. The wet cake was dried under vacuum at 50° C. for 9 hours to obtain 291.6 g of benzethonium heparinate. Benzethonium content as measured by HPLC was 71.4%.
• Step b 50 g of benzethonium heparinate (obtained in step (a)) and 189.6 g of DMF were fed into a suitable reactor and stirred for dissolution at room temperature, then was added 22.0 g of benzyl chloride and stirred the reaction mass for 10 hours. Heparin benzyl ester was precipitated by quenching the reaction mixture by adding 220.0 g of water at 15 to 20° C. allowed to stand and decanted the supernatant to retain heparin benzyl ester as wet solid in the reactor.
• benzethonium heparinate obtained in Example 1, step (a)
• 189.6 g of DMF were fed into a suitable reactor and stirred for dissolution at room temperature, then was added 22.0 g of benzyl chloride and stirred the reaction mass was then stirred for 15 hours.
• Heparin benzyl ester was precipitated by quenching the reaction mixture by adding 220.0 g of water at 10 to 20° C., allowed to stand and decanted the supernatant to retain heparin benzyl ester as wet solid in the reactor.
• Step a 1718 g of water and 275 g of benzethonium chloride were fed into a round bottom flask and stirred till dissolution at room temperature. 1000 g of water and 100 g of heparin were fed into another round bottom flask and stirred for dissolution. A solution of benzethonium chloride in water was added slowly to heparin solution and maintained for 2.5 hours. Then the mass was filtered, and the cake obtained was washed water repeatedly. The wet cake was dried under vacuum at 50° C. for 9 hours to obtain 291.6 g of benzethonium heparinate. Benzethonium content as measured by HPLC was 71.4%.
• Step b 70 g of benzethonium heparinate obtained in step (a) and 265.44 g N, N-dimethylformamide were fed into a round bottom flask and stirred, followed by the addition of 21.17 g of benzyl chloride slowly and the reaction mass was then stirred for 7 hours at room temperature.
• Step c Heparin benzyl ester was precipitated by quenching the reaction mixture by adding 308.0 g of water at 10 to 20° C., allowed to stand and decanted the supernatant to retain heparin benzyl ester as wet solid in the reactor.
• Step d The wet solid obtained in step (c) was washed with a solution of 10% sodium acetate in methanol followed by methanol, filtered and dried to yield 21.2 g of heparin benzyl ester sodium salt. Benzyl alcohol content of the ester obtained was 7.4%, measured by HPLC.
• Step e 10.0 g of the heparin benzyl ester sodium salt obtained in step (d) was suspended in 297 ml of purified water and heated under agitation to 60° ⁇ 1° C., followed by the addition of 33 ml of 1N sodium hydroxide solution. The contents were stirred at 60° ⁇ 1° C. for 60 minutes.
• Step f The solution obtained in step (e) was cooled to room temperature and pH was adjusted to 9.7 ⁇ 1 with 1N hydrochloride acid. Added 4.0 ml of 30% hydrogen peroxide solution and the mixture was stirred for 60 minutes by maintaining the pH constantly at 9.7 ⁇ 1 by adding 1N sodium hydroxide solution. Then the pH was readjusted to 6.0 ⁇ 0.1 with 1 N hydrochloride acid and sodium chloride was added to the reaction mixture in a quantity sufficient to achieve 10% (w/v). The product was precipitated by adding 3.6 volumes of methanol, filtered and dried under vacuum at 55° C. for 9 hours to obtain 7.03 gm of crude enoxaparin sodium.
• Step g The crude enoxaparin sodium (5 gm) obtained in step (f) was suspended in 50 ml of purified water and dissolved. Added 5 gm of sodium chloride and stirred. The product was precipitated by adding 150 ml of methanol, filtered and dried under vacuum at 55° C. for 9 hours to obtain 4.39 gm of enoxaparin sodium.
• Step h Charged 75 mL of water followed by 8.33 mL of ethanol in to a 100 mL 3 neck round bottom flask. To this, Enoxaparin sodium obtained in step (g), was added and stirred for dissolution, filtered the solution through 0.22 ⁇ filter and loaded the solution in lyophilization trays and freeze-dried to obtain Enoxaparin sodium in powder form (4.2 gm).
• Enoxaparin sodium met the United States Pharmacopoeial requirement as well as sameness criteria with respect to equivalence of physicochemical properties, mode of depolymerisation and equivalence in disaccharide building blocks, fragment mapping, and sequence of oligosaccharide species.

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